GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC B1380: Device Ignition ACCESSORY Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

B+ Terminal 4

B1370, B1380, B1385

B1370, B1380, B1385*

B1370, B1380, B1385

B+ Terminal 6

B1370, B1380, B1385

B1370, B1380, B1385*

B1370, B1380, B1385

Ignition Terminal 3

B1370

B1370

B1370

Ignition Terminal 5

B1380

B1380

B1380

Ignition Terminal 7

B1385

B1385

B1385

* An open/high resistance in this circuit may not cause this DTC depending on the ignition switch position when the open/high resistance occurred.

Circuit Description

The body control module (BCM), monitors the ignition 3, crank voltage, and ignition 1 circuits from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A 12 volt reference voltage is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for power mode signal discrimination. When the operator places the ignition switch in the Run or Accessory position, the ignition 3 circuit delivers the signal to the BCM.

Conditions for Running the DTC

    • The BCM must be powered and must detect a change in the ignition switch circuit states.
    • The vehicles battery must be fully charged.

Conditions for Setting the DTC

The BCM detects that the ignition 3 signal is shorted to ground, voltage, or open in the current ignition cycle.

Action Taken When the DTC Sets

    • The BCM stores DTC to memory.
    • The BCM operates in a fail-safe power mode dependent on the last valid power mode detected and the state of the engine run flag data on the class 2 serial data communications circuits.
    • The other modules on the vehicle operate in a fail safe power mode dependent on the last valid power mode transmitted by the BCM and the state of the engine run flag on the class 2 serial data communications circuits.

Conditions for Clearing the DTC

    • A current DTC clears on the next malfunction free cycle.
    • A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Reference Information

Schematic Reference

Power Moding Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Power Mode Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

With a scan tool, access BCM, Power Mode data display list and compare all parameters listed with the corresponding ignition key position. The PMM Power Mode Parameters table below illustrates the correct state of these input parameters in correspondence to the ignition switch position.

If any parameters are incorrect in any key position, refer to the Circuit/System Testing or Component Testing.

PMM Power Mode Parameters

Ignition Switch Position

Starter Switch

Accessory Switch

Ignition Run Start Switch

Operating Conditions: Drivers door open to disable RAP

Off

Released

Inactive

Inactive

Accessory

Released

Active

Inactive

Run

Released

Active

Active

Start

Cranking

Inactive

Active

Circuit/System Testing

    Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

  1. Connect a test lamp between each fuse test terminal of the ignition switch B+ circuit fuse and ground. The test lamp should illuminate.
  2. If the test lamp does not illuminate, test the ignition switch circuits listed below for a short to ground. If all circuits test OK, replace the BCM.
    • B+ terminal 4
    • B+ terminal 6
    • Ignition terminal 3
    • Ignition terminal 5
    • Ignition terminal 7
  3. Disconnect the harness connector at the ignition switch.
  4. Connect a test lamp between the ignition switch terminals listed below and ground. The test lamp should illuminate.
  5. If the test lamp does not illuminate, test the B+ circuit for an open/high resistance.
    • B+ terminal 4
    • B+ terminal 6

    Important: The ignition switch component test must be performed before proceeding with this test to verify the integrity of the switch.

  6. Perform the ignition switch component test. Verify the switch passes the test.
  7. If the ignition switch does not test normal, replace the ignition switch.
  8. Disconnect the X1 harness connector at the BCM, test for less than 1.0 volt between the circuit terminals of the BCM listed below and ground:
  9. • B+ terminal 25
    • Ignition terminal 21
    • Ignition terminal 22
    • Ignition terminal 23
    If greater than specified, test the circuit for a short to voltage.
  10. Test for less than 1.0 ohm between the BCM and the ignition switch on the circuits listed below:
  11. • B+ terminal 25, X1 and 4
    • B+ terminal 25, X1 and 6
    • Ignition terminal 21, X1 and 5
    • Ignition terminal 22, X1 and 7
    • Ignition terminal 23, X1 and 3
    If greater than specified, test the circuit for open/high resistance.
  12. If all circuits test normal, replace the BCM.

Component Testing

Ignition Switch

Using the Resistance Test below, check the resistance between the terminals of the ignition switch listed in each switch position listed.

If any reading is other than specified, replace the ignition switch.

Resistance Test

Ignition Switch Position

Terminals 5 and 6

Terminals 4 and 6

Terminals 3 and 4

Terminals 4 and 7

Off

Infinite

Infinite

Infinite

Infinite

Accessory

Infinite

Infinite

< 5.0 ohms

Infinite

Run

Infinite

Infinite

< 5.0 ohms

< 5.0 ohms

Start

< 5.0 ohms

Infinite

Infinite

< 5.0 ohms

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

    •  Ignition and Start Switch Replacement
    •  Control Module References for module replacement, setup, and programming